In the following description, the term “yarn” is intended to also include the threads, tapes, profile tapes, fibrillated tapes and slit-film bands of various linear mass density, diameter, width and thickness. The term “bobbin” is intended to include any metallic or non-metallic tubes on which the yarn is wound to form a suitable package. The term ‘yarn’ is also used to describe yarn with multiple threads or ends that a single winder might receive.
Automatic turret type winders are used in production or take-up process of continuously advancing yarn, for example, in yarn extrusion machines or in rewinding process for making plurality of small size yarn packages from a large yarn package. In general, the turret type automatic winders are positioned side by side in the horizontal direction and stack one above the other in vertical direction. The number of winding positions is exemplary both in horizontal row and vertical row.
The yarn transfer operation is important in the automatic yarn winding operation. If the yarn is not transferred in the first attempt, the continuously advancing yarn gets wasted until it is rethreaded. Worse still, the continuously advancing yarn, if not controlled properly in case it fails to transfer onto the empty bobbin, may interfere with the other yarn winders on the same machine and cause the entire machinery to stop which results in a huge amount of wastage, machine downtime and economic loss. In the worst situations, some parts of the machinery may get damaged.
In automatic turret type winders, a continuously advancing yarn is generally wound on an initially empty bobbin to form a suitable yarn package. When the pre-determined package size (length/diameter/time) is achieved on a bobbin installed on one of the bobbin holders, generally known as a spindle, the continuously advancing yarn is transferred by an automatic transfer device to an empty bobbin installed on another spindle to make a new yarn package without interrupting the winding operation. During the bobbin changeover operation, the empty bobbin is positioned in the path of the advancing yarn by rotating the turret. The continuously advancing yarn is then guided onto a yarn grasping device or a catching device by axially shifting or displacing the bobbin spindle or the traversing unit, such that the yarn is clamped at grasping device and then laid across the empty bobbin. Simultaneously, the yarn connecting the bobbin under winding and the full bobbin is severed.
While most of these known devices for transferring the yarn to the grasping device function satisfactorily, some of them, such as the one disclosed in EP 03725171 involves complex mechanisms of achieving yarn transfer by movement of the entire cam box that houses the traversing mechanism. This type of mechanism involves the axial displacement of large mass leading to complex, expensive device. Therefore, there is a need to provide simpler, reliable mechanism of introducing advancing yarn into a grasping device during the bobbin changeover operation in automatic winder.